Testing apparatuses for evaluating semiconductor devices are equipped with sockets for receiving semiconductor devices. Depending on types of semiconductor devices and types of evaluation testing (burn-in test, prober test, final test or the like), a variety of types of sockets are employed. For instance, ICs, which are typical of semiconductor devices, may be of a type having lead pins thereof extending downward from a lower face of an IC body. For this kind of ICs, an IC socket having an IC mounting section is employed. The IC mounting section is provided in an upper face of the socket to which a lower face of the IC is joined. Such an IC mounting section generally includes pairs of contact pieces which are the same in number as IC lead pins. In mounting the IC to the IC socket, each IC lead pin is inserted between a corresponding pair of contact pieces. For another type of ICs having lead pieces extending laterally from side faces of an IC body, an IC socket having an IC socket body provided at its central part with an IC accommodation space is employed. The IC socket of this kind typically includes contact pieces disposed around the IC accommodation space. The contact pieces are the same in number to the IC lead pieces. Distal end portions of the contact pieces extend obliquely downward from above the IC, received in the accommodation space, toward the IC lead pieces. In mounting the IC to the IC socket, a lid member of the IC socket, disposed to face the IC inserted into the accommodation space of the socket body, is moved toward the IC, causing the distal end portions of the contact pieces to move downward. Distal end faces of the contact pieces are brought in contact with upper flat faces of the distal end portions of the IC lead pieces, whereby electrical connection between the IC and the IC socket is established.
Foreign substances, such as dust flying from the outside and solder peeling off IC leads, are liable to adhere to contact pieces or contact pins (hereinafter referred to as contact pins) of the IC socket. Foreign substances adhered thereto cause contact failure or electrical short-circuit between the IC leads and the contact pins, preventing intended evaluation testing. Thus, foreign substance removal process, such as blowing of pressurized air to the contact pins, is implemented before mounting the IC to the IC socket. However, it is difficult to fully remove minute foreign substances from the contact pins.
Generally, the lead pieces or the lead pins (hereinafter referred to as IC leads) of the IC are plated with solder, and the contact pins of the IC socket are plated with gold. To carry out the evaluation testing, ICs serving as testing objects are sequentially mounted to the IC socket. When the IC leads are in contact with the contact pins of the IC socket, solder is transferred from the IC leads to the contact pins. As the evaluation testing is implemented in respect of a number of ICs, the transition of solder from the IC leads to the contact pins is repeated, so that deposition of solder on the surfaces of the contact pins gradually progresses, and solder components diffuse into the gold-plated surfaces of the contact pins, forming a diffusion layer therein. With elapse of time, the diffusion layer is subject to oxidization, forming an oxide film layer which increases the electrical resistance between the contact pins and the leads. The formation of the oxide film layer progresses with the increase in number of times of using the IC socket, so that normally operable ICs may be erroneously determined as faulty products in the evaluation testing.
To remove foreign substances such as solder or oxide film adhered to the contact pins of the IC socket, cleaning such as air-blowing, ultrasonic-cleaning, or brushing is implemented when the IC socket is used a predetermined number of times or for a predetermined time period. However, by means of cleaning of these kinds, it is difficult to fully remove the foreign substances.
This necessitates early replacement of the IC socket which is high-priced. Upon replacement of the IC socket, a printed circuit board on which the IC socket is mounted must be generally detached from the testing apparatus, together with the IC socket. A lot of time is required to dismount the IC socket from the printed circuit board and to mount a new IC socket thereon. Thus, backup printed circuit boards each mounted with an IC socket must be prepared to continuously operate the testing apparatus.
JP-A-10-82826 discloses a cleaning technique other than the above-mentioned techniques such as air-blowing. A cleaning method and apparatus disclosed therein are applied solely to cleaning of IC sockets of a type adapted for ICs each having lead pins extending from the lower face of its body. The IC socket of this kind has pairs of contact pieces provided on its face at which it is joined to the IC. Each contact piece pair permits a corresponding IC lead pin to be detachably inserted therebetween. In the cleaning, a cleaning head instead of the IC serving as a testing object is moved from above the IC socket and is joined to the upper face of the IC socket. Each cleaning pin (file-like grinding portion) of the cleaning head is inserted between a corresponding contact piece pair of the IC socket, to remove foreign substances adhered thereto. In this manner, the cleaning technique disclosed in the above-mentioned publication teaches technical concept for removing foreign substances adhered to the contact pieces in term of grinding. However, this cleaning technique is solely applicable to the cleaning of IC sockets suited to ICs having lead pins extending from the lower face of the IC body. Since the cleaning head comprises the cleaning pins which are formed with file-like grinding portions and which are the same in number to the IC lead pins, the cleaning head is not simple in construction and is hence high-priced. In addition, the contact pieces of the IC socket can be excessively worn in term of grinding by means of the file-like grinding portions.
In an apparatus and method disclosed in JP-A-6-314899 for mounting and dismounting a semiconductor device, an IC is transferred, before being mounted on an IC socket, toward a cleaning board which is separate from and disposed to face a testing board (testing apparatus) mounted with the IC socket. By doing this, IC leads are in contact with a file layer formed in the cleaning board, whereby foreign substances adhered thereto are removed. The apparatus and method disclosed in this publication merely contemplate cleaning IC leads, and are not applicable to removal of foreign substance from the contact pins of the IC socket. Further, the IC is required to be positioned on the cleaning board for removal of foreign substances and then positioned on the IC socket, so that a positioning control is not simple. Furthermore, the cleaning board and an installation space therefor are required. This increases cleaning costs. In addition, even if this cleaning technique could be applied to the removal of foreign substances from the contact pins, the IC socket is still required to be dismounted from the testing apparatus upon removal of foreign substances. The need of dismounting the IC socket entails the above-mentioned drawbacks. Further, the cleaning using a file layer may excessively wear the contact pins of the IC socket.
JP-A-7-234262 discloses a method and apparatus for cleaning an IC socket in which the IC socket having been employed for evaluation testing is dismounted from a testing apparatus, and then electrodes (contact pins) of the IC socket are immersed into acidic medical fluid, to thereby remove solder adhered to the electrodes. The cleaned IC socket is mounted to the testing apparatus. According to this IC socket cleaning technique, the IC socket must be detached from the testing apparatus upon removal of solder from the contact pins. Moreover, in order to chemically remove the adhered solder with use of medical fluid, a large-scale arrangement is generally required.